In the 3GPP (Third Generation Partnership Project) that defines a standard for mobile network systems, an EPC (Evolved Packet Core) is specified as the next generation mobile network system. The EPC is a network system that accommodates an LTE (Long Term Evolution) access network in addition to wireless access networks called the second generation and the third generation.
Incoming packet call processing in the EPC is described hereinafter. In Non-Patent Literature 1, incoming packet call processing in the case where a UE (User Equipment) representing a user terminal is in the idle mode is disclosed. The state where the UE is in the idle mode is the state where the UE is not connected with the EPC. In other words, a radio bearer between the UE and the EPC is disconnected in this state. In such a case, when an incoming packet call is made to the UE, an SGW (Serving Gateway), which is a bearer management device, sends an incoming call notification message to an MME (Mobility Management Entity) or an SGSN (Serving GPRS Support Node) that manages the UE. Receiving the incoming call notification message, the MME or SGSN sends a Paging message to an eNB (evolved Node B) or a NodeB, which is a base station, in order to call the UE. Receiving the Paging message, the eNB or NodeB performs Page processing on a plurality of UEs located in the area managed by itself. The UE to be called sends a response message to the eNB or NodeB and connects to the EPC.
In this manner, even when an incoming packet call is made to the UE in the idle mode which is not connected with the EPC, it is possible to perform data communication with the UE by calling the UE from the network side.